The invention relates to a controller for a communication network.
An example of a structure of (at least part of) a conventional base station is shown in FIG. 1. The base station 101 comprises a network layer 102 and a control layer 103, which controls the operation of a radio 104. The network and control layers are usually implemented in software. The radio is comprised of a layer of embedded firmware 105, a MAC layer 106 and a physical layer 107. The firmware receives data from the control layer which it formats into frames for passing to the MAC. The MAC is suitably implemented as memory-mapped hardware. The MAC may perform the RF modulation that is required before the physical layer transmits the frame over the air interface.
A problem with the structure shown in FIG. 1 is that the embedded firmware has to be written in a low-level programming language, which makes it difficult and time-consuming to program, test and debug. Another problem is that the firmware tends to be machine-specific, so that it cannot be readily transferred from one device to another. This may make it difficult to deploy a large number of base stations in a number of different countries, because the firmware for those base stations will have to be specifically designed for the particular machines that are going to implement them.
A possible solution has been proposed in which the frame is not composed in the radio but elsewhere in the network. The frame is then transmitted over the network to the MAC, which is required to perform only minor formatting before the frame is ready for transmission. An advantage of this approach is that the formatting of the data to be transmitted is largely performed in software. A disadvantage is that the process of receiving and decoding data, processing that data to generate a response, and formatting the response for transmission causes a delay that can be unacceptable in modern networks designed to accommodate fast data rates. Therefore, there is a need for a flexible base station that is configured to be able to cope with the delays that formatting frames in software can cause.